Hello everyone,
I just put level streaming in the map and add level to it… then click build.
Build compete but lighting build stuck at 99% for half hour now. Use to be 2-3 min.
How can I fix it?
I have a same problem now 
Is there a fix to this problem?
That’s pretty normal for larger scenes.
You might want to check to see if you’re running out of ram and accessing the page file. Open your task manager and from there, open the resource monitor. Watch the hard drive tab and see if it’s accessing the pagefile.sys.
If it is, then it means you ran out of ram and the pagefile is exponentially slower than ram. That 99% is probably the part where it would have normally just read stuff from ram, but now has to read it from the super slow page file.
It’s normal when building in higher quality levels.
Lightmass doesn’t split the load among the multiple workers evenly, so depending on your scene all other threads can be done with their work sitting waiting for the one unlucky thread who ended up with the largest model in the scene.
It doesn’t matter how many threads or render nodes you have, the time for building the lighting is limited to how long one thread takes to light the most complex model in your scene.